如何通过所述列表中的Map属性值从DynamoDB地图列表中删除？

我有以下列表示例:

{
  "favorites": [
    {
      "createdAt": 1448998673852,
      "entityId": "558da3de395b1aee2d6b7d2b",
      "type": "media"
    },
    {
      "createdAt": 1448998789252,
      "entityId": "558da3de395b1aee2d6b7d83",
      "type": "media"
    },
    {
      "createdAt": 1448998793729,
      "entityId": "558da3de395b1aee2d6b7d99",
      "type": "media"
    },
    {
      "createdAt": 1448998813023,
      "entityId": "558da3de395b1aee2d6b7daf",
      "type": "media"
    }
  ],
  "userId": "2"
}

我想删除地图:"entityId": "558da3de395b1aee2d6b7d2b".

我正在考虑一个UpdateItem查询,我查看了REMOVE表达文档(http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.Modifying.html),但我似乎无法看到任何示例,除了通过索引值从List中删除项目....